Moisture barrier properties of xylan composite films
Moisture barrier properties of films based on xylan reinforced with several cellulosic resources including nanocrystalline cellulose, acacia bleached kraft pulp fibers and softwood kraft fibers have been evaluated. Measurements of water vapor transmission rate (WVTR) were performed by a modification of the wet cup method described by ASTM E 96-95, indicating that membranes with 10% nanocrystalline cellulose, prepared using a sulfuric acid, exhibited the lowest permeability value of 174 g mil/hm2 among the composite films studied. Both the acacia and the softwood kraft pulp fibers when used for xylan film formation exhibited higher water vapor transmission rates at addition levels of 50% and no improvement at lower levels of 5% and 10%, in comparison to control xylan films. Reinforcement of xylan with hydrochloric acid made nanocrystalline cellulose yielded films that showed a reduction in water transmission but the reduction was not as significant as with the reinforcement of xylan with sulfuric nanocrystalline cellulose. The results showed that xylan films reinforced with 10% sulfuric nanocrystalline cellulose exhibited reductions in water transmission rates of 362%, 62% and 61% over films prepared with 10% softwood kraft fibers, 10% acacia fiber and 10% hydrochloric acid prepared nanocrystalline cellulose, respectively. The morphology of the resulting nanocomposite films was examined by SEM and AFM which showed that control films containing xylan and sorbitol had a more open structure as compared to xylan–sorbitol films containing sulfuric nanocrystalline cellulose. The results from FT-IR suggested strong interactions occurred between the nanocrystalline cellulose and the matrix.